Undercover police officer Mark Kennedy is at the centre of a growing international row over his actions. Photograph: Guardian

The international row surrounding the undercover police officer Mark Kennedy intensified today as politicians across Europe demanded information about his activities and new allegations surfaced about the scope of his sexual activity.

In a day of dramatic developments, Kennedy, the Metropolitan police officer at the centre of a growing controversy over the infiltration of peaceful environmental groups, emerged as a key figure in protest movements spanning several European countries, including Ireland, Iceland, Germany, Italy and Spain.

"Kennedy wanted to infiltrate anti-fascists, and as an agent provocateur to instigate actions together with them. I suspect then, that it wasn't Scotland Yard that focused his interest on the 'hot spots' of the German anti-fascist scene. I see proof instead of the opposite, that the German police were involved in the operation of this British agent."

In Ireland Labour foreign affairs spokesman Michael D Higgins called on the minister for justice Dermot Ahern to issue a statement on Kennedy's activities after it emerged he had travelled to the country at least five times between 2004 and 2006, linking up with activists in Dublin, Cork and Mayo.

One Irish activist, who met Kennedy several times and who put him up in Dublin in 2006, said the undercover officer acted as a "facilitator" between different protest groups from Ireland the UK and Iceland: "He did a lot with logistics because he had a van and helped move stuff around a lot," said the man who did not want to be identified. "He was not a major strategist but he was very good at linking people and different groups together."

Kennedy also spent time in Iceland forging close links with the Saving Iceland campaign group. He introduced members of this group to activists in Ireland and in the summer of 2005 he attended a gathering of direct action campaigners in Reykjavik. Jason Kirkpatrick, a documentary film-maker and former friend of Kennedy's, said he returned from the trip boasting he had been there training other activists in direct action techniques.

"He showed me a video of him training people in lock-down techniques," said Kirkpatrick, who lives in Germany. "The Icelandic protesters had asked for help from the movement in the UK and Mark was one of the ones that went over to train people. I remember he was laughing about the Icelandic police because they had never seen protesters locked to lorries before and the police did not know what to do."

Kennedy also spent time in Spain, France and Italy sometimes travelling under the guise of a "freelance climber" at other times openly connected to Dissent!, an international network of local groups organising opposition to the G8 summit at Gleneagles, Perthshire, in July 2005.

It is during these trips that he is alleged to have had several sexual relationships with other activists. Today Jean, 36, an environmental activist based in France who met Kennedy several times, told the Guardian: "It is well known in the movement that Kennedy slept with a large number of women who didn't know he was a police officer, and he therefore had sex with them without their informed consent. It happened in Britain and across Europe over several years and some of the women were friends of mine.

"There is a profound moral question here, and possibly legal questions as well," she added. "The question for senior police officers in the UK is simple: how much did they know and when did they know it?"

Kennedy also paid for several campaigners to travel to Ireland in the spring of 2005 and then to Germany to discuss the upcoming G8 protests, according to another activist.

According to a long term former friend Kennedy's last appearance as an activist was during an animal rights protest in Milan in September last year when he gave a climbing workshop for fellow protesters.

• This article was amended on 13th January 2011 to remove a quote subsequently found to be based on inaccurate information